PB1778: PAN-PIM KINASE INHIBITOR PIM447 SHOWS SUPERIOR ANTI-LEUKEMIC EFFECT IN ACUTE ERYTHROID LEUKEMIA
Authors: Chi-Yang Tseng, Ya-Chu Yu, Yu-Hsuan Fu, Da-Liang Ou, Liang-In Lin
Journal: HemaSphere (2023)

Topic: 3. Acute myeloid leukemia - Biology & Translational Research Background: The PIM1 (Proviral Integration site for Moloney murine leukemia virus-1) is engaged with various biological activities including cell growth, apoptosis inhibition, drug resistance, and transcription activation. We analyzed the acute myeloid leukemia (AML) cohort from the TCGA database by using UALCAN and demonstrated that AML patients with high PIM1 expression had poor prognosis. In addition, PIM1 was highly expressed in AML patients with M6. These results suggested that PIM1 could be a potential therapeutic target in AML. PIM447 (LGH447) is a potent pan-PIM kinase inhibitor. Aims: To evaluate the efficacy and the anti-leukemic mechanism of PIM447 on acute erythroid leukemia cell HEL92.1.7 from both in vitro and in vivo aspects. Methods: HEL 92.1.7, Kasumi-1, THP-1, OCI-AML3, Molm-13 myeloid leukemia cell lines were used. PIM477 was purchased from Selleckchem for in vitro and in vivo study. The CAnN.Cg-Foxn1nu/CrlNarl nude mice were for in vivo study. RNA-seq was performed by an Illumina NovaSeq 6000 platform. Differentially expressed genes (DEGs) were identified by EBseq with a threshold of p < 0.05. The ATP production rate was analyzed by Seahorse XF ATP Real-Time rate assay. Flow cytometry was used for cell cycle, apoptosis, and mitochondrial analysis. Results: Both qRT-PCR and immunoblotting showed that HEL 92.1.7 cells had the highest expressed PIM1 in a panel of AML cell lines. Among these AML cell lines, HEL 92.1.7 cells had the lowest IC50 of 0.66 μM to PIM447, a dose much lower than plasma level of 3.1 μM. In addition, PIM447 could significantly decrease the phosphorylation of mTOR, p70-S6K, and 4E-BP1 in HEL 92.1.7 cells. To assess additional molecular mechanism of PIM447, RNA-seq was performed. A total of 119 (77 upregulated and 42 downregulated) DEGs were identified in the transcriptomic signature difference between PIM447-treated and DMSO-treated HEL 92.1.7 cells. Gene Set Enrichment Analysis indicated that the downregulated pathways in PIM447-treated cells included cell cycle, mTOR signaling, and protein synthesis. In addition, oxidative phosphorylation and several mitochondrial-related pathways were also downregulated in PIM447-treated HEL 92.1.7 cells. Further, PIM447 could significantly suppress cell proliferation, induce G0/G1 cell cycle arrest, and increase apoptosis in HEL 92.1.7 cells. Moreover, PIM447 could significantly inhibit mitochondrial ATP production in HEL 92.1.7 cells by using Seahorse XF ATP Real-Time rate assay. Finally, we found that PIM447 could not only significantly decrease membrane potential, mtDNA, and mitochondrial mass, but also increase mitochondrial ROS in HEL 92.1.7 cells. In vivo studies revealed that the oral administration of a 0.5 or 5 mg/kg of PIM447 could suppress HEL 92.1.7 tumor growth and extend mice survival time without causing significant weight changes. Summary/Conclusion: PIM447 was effectively cytotoxic to acute erythroid leukemia cell line HEL92.1.7. Transcriptomic analysis and further experiments showed that PIM447 could suppress cell proliferation, induce cell cycle arrest, increase apoptosis, and damage mitochondria in HEL92.1.7 cells. In vivo xenograft model experiment demonstrated that PIM447 could retard HEL92.1.7 tumor growth. This information highlights potential therapeutic strategy targeting PIM1 in patients with acute erythroid leukemia. Clinical trials evaluating the efficacy of PIM447 in acute erythroleukemia are warranted. Keywords: Pim-1, Myeloid leukemia, Kinase inhibitor